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. 2010 Apr 13;5(4):e10138.
doi: 10.1371/journal.pone.0010138.

COPD and the risk of tuberculosis--a population-based cohort study

Malin Inghammar  1 , Anders Ekbom, Gunnar Engström, Bengt Ljungberg, Victoria Romanus, Claes-Göran Löfdahl, Arne Egesten
Affiliations

COPD and the risk of tuberculosis--a population-based cohort study

Malin Inghammar et al. PLoS One. .

Abstract

Background: Both chronic obstructive pulmonary disease (COPD) and tuberculosis (TB) primarily affect the lungs and are major causes of morbidity and mortality worldwide. COPD and TB have common risk factors such as smoking, low socioeconomic status and dysregulation of host defence functions. COPD is a prevalent co-morbid condition, especially in elderly with TB but in contrast to other diseases known to increase the risk of TB, relatively little is known about the specific relationship and impact from COPD on TB-incidence and mortality.

Methods and findings: All individuals > or = 40 years of age, discharged with a diagnosis of COPD from Swedish hospitals 1987-2003 were identified in the Swedish Inpatient Register (n = 115,867). Records were linked to the Swedish Tuberculosis Register 1989-2007 and the relative risk of active TB in patients with COPD compared to control subjects randomly selected from the general population (matched for sex, year of birth and county of residence) was estimated using Cox regression. The analyses were stratified by year of birth, sex and county of residence and adjusted for immigration status, socioeconomic status (SES) and inpatient co-morbidities previously known to increase the risk of TB. COPD patients had a three-fold increased hazard ratio (HR) of developing active TB (HR 3.0 (95% confidence interval 2.4 to 4.0)) that was mainly dependent on an increased risk of pulmonary TB. In addition, logistic regression estimates showed that COPD patients who developed active TB had a two-fold increased risk of death from all causes within first year after the TB diagnosis compared to the general population control subjects with TB (OR 2.2, 95% confidence interval 1.2 to 4.1).

Conclusions: This population-based study comprised of a large number of COPD patients shows that these patients have an increased risk of developing active TB compared to the general population. The results raise concerns that the increasing global burden of COPD will increase the incidence of active TB. The underlying contributory factors need to be disentangled in further studies.

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Conflict of interest statement

Competing Interests: Claes-Göran Löfdahl has been paid for lectures by AstraZeneca, Boehringer-Ingelheim, GlaxoSmithKline and Pfizer; taken part and been paid for ad hoc advisory boards for the same companies; and has had institutional support as unrestricted grants from AstraZeneca, Boehringer-Ingelheim, and GlaxoSmithKline. This study has in some parts been funded by a commercial funder, but that does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Flow chart demonstrating the study design.
1 = Identification of patients with COPD in the inpatient register, 2 = identification of their population controls (matched for age, sex and county of residence), 3 = Register linkage for vital status, inpatient co-morbidity, socio-economic position, prior and incident TB.
See this image and copyright information in PMC

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